I cannot but agree with Ridge Runner that the 5.3 Eclipse coil could be looked upon as a must have for the MXT. In a word superb, it will outperform the 6x4dd in all but the most extreme ground. It probably punches much deeper than the 10 x 6 dd a lot of the time.
That 10 x 6 dd could be looked upon as a very good Jack of all trades, but an expert at none. The introduction of the round 10" dd has taken the shine off the 10 x 6 dd no doubt..
The almost forgot Eclipse 9.5 is also superb, the dry sand performance is outstanding. It is sensitive to the smallest targets and is very very deep.
It outperforms all my White's coils under the right conditions. It is not good in hot hot ground, but you can lift the coil a tad higher than normal and boost gain in hot ground to stay in the game. Sometimes it works surprisingly well.
If prospecting mode gets noisy, switch to relic with 1 or 2 disc, again it works well.
In EXTREME ground the 6x4 dd and 14 x 8 dd allow me to continue to search. They have their own niche. When the ground is beyond noisy that little 6x4 dd's inherit characteristics combined with a very small footprint mean it suffers less from mineralization. Allowing the hunt to continue at a painfully slow pace.
If the ground will let you the 9.5 and 5.3 Eclipse coils are, I'll say it again: superb.
Just like to add that ALL my MXT coils are second hand, purchased from UK, Australia, USA and Canada... Slowly over many years when bargains and opportunities presented themselves.. just cannot afford to buy new.
I also recommend 'The MXT Edge' by Jeff Foster if you operate this outstanding metal detector.
My 2 cents worth, all the best.